Joe Elliott of Def Leppard is the latest music industry veteran to share his take on Taylor Swift’s influence.

The rock vocalist made a bold declaration about the extent of the megastar’s popularity during a recent conversation with Billboard published just one week after the release of Swift’s 11th studio album, The Tortured Poets Department. The project arrived as a surprise double album on April 19 and has already shattered streaming records in the days since its release.

During his conversation with the magazine, Elliott and Def Leppard bassist Rick Savage, who also participated in the interview, were asked about a time in 2009 when Def Leppard united with the “Anti-Hero” singer on CMT Crossroads.

Savage, 63, said Swift, 34, was already “pretty big” at the time, though he acknowledged her popularity was “not to the level she’s at now.”

Elliott, 64, then spoke of Swift’s history with Def Leppard’s music, explaining that her mother, Andrea, was a fan of theirs when she was pregnant with Swift—and thus Swift was essentially listening to some of their music “in the womb.” When they met for Crossroads, Elliott said the band “became fans of her” just as she was of them.

“I think we’d all be lying if we said we knew she was going to become as big as she has because she’s actually become bigger than anything that’s ever been before,” Elliott said. He then suggested that Swift is now “probably bigger than The Beatles and The [Rolling] Stones combined, for her generation of fans” before adding that she has “taken success to a level that is unheard of.”

The bandmates both came away from their 2009 collaboration with Swift with positive thoughts about the “Cruel Summer” singer. “It was a really great experience working with her and the band,” Savage told the magazine, as Elliott said he hopes she “works with us again one day.”